1. Field of the Invention
This invention relates generally to the field of semiconductor fabrication. More specifically, the invention relates to a method of cleaning undesired substances from at least one surface of a semiconductor processing chamber.
2. Background of the Invention
Deposition of materials onto a silicon substrate, either through Chemical Vapor Deposition (“CVD”) or through Atomic Layer Deposition (“ALD”), are common steps in the manufacture of integrated circuits. Due to the nature of these deposition techniques, the material intended to be deposited on the substrate is often also inadvertently deposited on surfaces within the semiconductor processing chamber. These inadvertent deposits of undesired material on the various surfaces of the semiconductor processing chamber must be periodically cleaned; otherwise they may accumulate or affect later deposition stages performed in the same chamber. Periodic cleaning of the entire chamber is therefore necessary to maintain high product quality, and it is preferable for a cleaning process to have a high cleaning rate so as to keep tool downtime at a minimum and maximize tool throughput.
Several methods of chamber cleaning are known. Wet chemical cleaning of the chamber is possible, but as it requires the disassembly of the reaction chamber, it requires high labor costs and long downtime. So called dry cleaning involves introducing a gas mixture into the chamber, which reacts with the undesired substances, and which then is easily removed through a purging step. Some dry cleaning methods employ microwave generated plasmas in the chamber to disassociate the gas mixture into reactive species that clean the deposited materials through chemical reaction. When a plasma is required, areas in the chamber that are not in direct contact with the plasma will not be effectively cleaned. Also, over time the plasma may negatively affect the chamber's condition by causing damage or deterioration of the chamber and any components stored within.
In the absence of a plasma, it is possible to increase the chamber temperature so as to attempt to promote the thermal disassociation of the cleaning gas mixture. This high temperature type cleaning is less commercially feasible as heating the chamber increases the overall cleaning step downtime, and may also damage the chamber and components stored within. For instance, it may take a considerable amount of time to heat the chamber to a temperature at which the cleaning gas mixture will disassociate, and then afterwards, it may also take a considerable amount of time to cool the chamber back to a suitable temperature for the requisite manufacturing process.
Another method is to introduce a cleaning gas mixture which has previously been mixed, disassociated, and stored in a storage vessel. However, such premixed cleaning gases normally face limits in the amount of volume/pressure under which they can be stored or transported. Further, introducing such a premixed cleaning gas source may require multiple cylinder changes which increases over all safety concerns for operators of such systems.
Consequently, there exists a need for a chamber cleaning method which does not require a plasma in the chamber, which can be performed at relatively low temperatures, which decreases the amount of time during which the chamber is cleaned, and which decreases overall safety concerns.